If you are trying to switch from Chrome, then just use regular Firefox with the ublock extension (and maybe some of the other privacy extension officially supported). If you are a "power user" and want modify/access about:config and other settings then you need Firefox Nightly. The Fennec and Fenix (iirc) are just stripped down Firefox that either only have private mode or additional settings for privacy (that are already present in regular version, but way not be enabled by default). Hope that helps.

Just get the regular Firefox with uBlock Origin if all you're concerned about are advertisements. The default settings out of the box are fine for most users.

Get the Mull browser if you're concerned about privacy as well, as this is a hardened Firefox similar to LibreWolf. Not sure if this is on the Play Store, but it's definitely on F-Droid.

Using since few months Iceraven Browser with ublock origin and no-script addons

I liked IceRaven, but it's not regularly updated anymore. I would go with Firefox Nightly, since that lets you install any extension you want (through an arduous process), where regular Firefox only lets you install add-ons on Mozilla's approved whitelist.

Before jumping ship from Chrome completely try Vivaldi, it's built on the Chrome engine (so you can continue using your extensions and what nots) but it's made by one of the guys that created Opera but jumped ship before it got sold off to big money.

So like old Opera there's a huge emphasis on not only pushing what a browser can do (Opera pioneered speed dial for instance and tabs too iirc) but privacy and security as well.

I've been using it for a while now with Firefox really not being able to scratch the itch left by Opera and I'm really impressed with just how good it is for being built on Chrome.

I personally use Mull

I use Fennec it disables telemetry and updates pretty quickly from Firefox upstream releases. Also supports custom sync server and add-ons collection without having to run nightly builds.